This invention relates to shot peening and, more particularly, to shot peening a vehicle suspension component using ceramic peening media to increase fatigue properties of the suspension component.
Suspension components, such as coil springs, stabilizer bars, torsion bars, and the like, have considerable fatigue resistance to withstand repeated cycles of mechanical stress. For example, coil springs are manufactured from steel rods by heating and forming the rods into the desired coil shape. The coil springs are then heat treated and shot peened with steel particles to increase the fatigue resistance. The steel particles impact the surface of the coil spring, thereby compressing the surface and creating a residual compressive surface stress that offsets mechanical tensile stresses to resist fatigue.
Although using steel particles is effective for increasing resistance to fatigue, there are opportunities for improvement. For example, one problem related to the use of steel particles is that the steel particles wear the peening equipment at a rather quick rate. Depending on the frequency of use, portions of the peening equipment may require replacement over relatively short time intervals, which increase operating expenses.
Additionally, the level of fatigue resistance that is attainable using steel particles is limited. For example, using larger diameter steel particles would produce a greater amount of residual compressive surface stress. However, the gain in fatigue resistance from the greater residual compressive surface stress is offset by an increase in surface roughness due to impact with the larger diameter steel particles. Thus, steel particles have limited effectiveness for improving fatigue resistance.
Therefore, there is a need for a peening method that provides less wear on the peening equipment and produces suspension components having enhanced fatigue resistance. The disclosed examples address this need while avoiding the shortcomings and drawbacks of the prior art.